KANDAHAR  - Four Nato troops - believed to be Americans - were killed when a helicopter responding to a suicide attack in southern Afghanistan crashed, military and Afghan officials said Friday.

Nato’s International Security Assistance Force (Isaf) confirmed the deaths, but did not disclose their nationalities or give any cause for the crash. A US defence official in Washington told AFP that those on board were likely American soldiers.

A senior police officer in Helmand province said the helicopter went down in stormy weather on a flight related to a deadly suicide attack on an Afghan police post in the province’s Garmser district.

“There was a suicide attack on a police checkpoint that killed four police and wounded seven others,” Mohammad Islamil Hotak told AFP, adding that it was unclear whether the helicopter was heading to the area in support or to pick up casualties.

Taliban insurgents claimed responsibility for the crash, saying on their website the aircraft was “shot down by a rocket attack by armed mujahideen fighters”. “Four US occupying forces were on board when the helicopter was shot down,” the statement said.

Hotak said there was “no proof” that the Taliban was responsible.

A US official said earlier that poor weather had likely been a factor in the incident, but cautioned that nothing was being ruled out.

And 30 US troops and eight Afghans were killed in August 2011 when Taliban insurgents shot down a Chinook helicopter, in the deadliest incident for US and NATO forces since the war in Afghanistan began in 2001.